Add the experimental sqlite3session_changeset_size() API.

FossilOrigin-Name: 3de544d495fee553d95fde3fb656745d633138115d25ed39760a1ea7c8c3fae6

src/sqlite.h.in

@@ -9546,6 +9546,15 @@ int sqlite3_db_cacheflush(sqlite3*);
 ** triggers; or 2 for changes resulting from triggers called by top-level
 ** triggers; and so forth.
 **
+** When the [sqlite3_blob_write()] API is used to update a blob column,
+** the pre-update hook is invoked with SQLITE_DELETE. This is because the
+** in this case the new values are not available. In this case, when a
+** callback made with op==SQLITE_DELETE is actuall a write using the
+** sqlite3_blob_write() API, the [sqlite3_preupdate_blobwrite()] returns
+** the index of the column being written. In other cases, where the
+** pre-update hook is being invoked for some other reason, including a
+** regular DELETE, sqlite3_preupdate_blobwrite() returns -1.
+**
 ** See also:  [sqlite3_update_hook()]
 */
 #if defined(SQLITE_ENABLE_PREUPDATE_HOOK)
@@ -9566,6 +9575,7 @@ int sqlite3_preupdate_old(sqlite3 *, int, sqlite3_value **);
 int sqlite3_preupdate_count(sqlite3 *);
 int sqlite3_preupdate_depth(sqlite3 *);
 int sqlite3_preupdate_new(sqlite3 *, int, sqlite3_value **);
+int sqlite3_preupdate_blobwrite(sqlite3 *);
 #endif
 
 /*

src/vdbe.c

@@ -5080,7 +5080,7 @@ case OP_Insert: {
   /* Invoke the pre-update hook, if any */
   if( pTab ){
     if( db->xPreUpdateCallback && !(pOp->p5 & OPFLAG_ISUPDATE) ){
-      sqlite3VdbePreUpdateHook(p, pC, SQLITE_INSERT, zDb, pTab, x.nKey,pOp->p2);
+      sqlite3VdbePreUpdateHook(p,pC,SQLITE_INSERT,zDb,pTab,x.nKey,pOp->p2,-1);
     }
     if( db->xUpdateCallback==0 || pTab->aCol==0 ){
       /* Prevent post-update hook from running in cases when it should not */
@@ -5240,7 +5240,7 @@ case OP_Delete: {
     sqlite3VdbePreUpdateHook(p, pC,
         (opflags & OPFLAG_ISUPDATE) ? SQLITE_UPDATE : SQLITE_DELETE, 
         zDb, pTab, pC->movetoTarget,
-        pOp->p3
+        pOp->p3, -1
     );
   }
   if( opflags & OPFLAG_ISNOOP ) break;

src/vdbeInt.h

@@ -472,6 +472,7 @@ struct PreUpdate {
   UnpackedRecord *pUnpacked;      /* Unpacked version of aRecord[] */
   UnpackedRecord *pNewUnpacked;   /* Unpacked version of new.* record */
   int iNewReg;                    /* Register for new.* values */
+  int iBlobWrite;                 /* Value returned by preupdate_blobwrite() */
   i64 iKey1;                      /* First key value passed to hook */
   i64 iKey2;                      /* Second key value passed to hook */
   Mem *aNew;                      /* Array of new.* values */
@@ -560,7 +561,8 @@ void sqlite3VdbeFrameMemDel(void*);      /* Destructor on Mem */
 void sqlite3VdbeFrameDelete(VdbeFrame*); /* Actually deletes the Frame */
 int sqlite3VdbeFrameRestore(VdbeFrame *);
 #ifdef SQLITE_ENABLE_PREUPDATE_HOOK
-void sqlite3VdbePreUpdateHook(Vdbe*,VdbeCursor*,int,const char*,Table*,i64,int);
+void sqlite3VdbePreUpdateHook(
+    Vdbe*,VdbeCursor*,int,const char*,Table*,i64,int,int);
 #endif
 int sqlite3VdbeTransferError(Vdbe *p);
 

src/vdbeapi.c

@@ -1905,6 +1905,17 @@ int sqlite3_preupdate_depth(sqlite3 *db){
 }
 #endif /* SQLITE_ENABLE_PREUPDATE_HOOK */
 
+#ifdef SQLITE_ENABLE_PREUPDATE_HOOK
+/*
+** This function is designed to be called from within a pre-update callback
+** only. 
+*/
+int sqlite3_preupdate_blobwrite(sqlite3 *db){
+  PreUpdate *p = db->pPreUpdate;
+  return (p ? p->iBlobWrite : -1);
+}
+#endif
+
 #ifdef SQLITE_ENABLE_PREUPDATE_HOOK
 /*
 ** This function is called from within a pre-update callback to retrieve

src/vdbeaux.c

@@ -5189,7 +5189,8 @@ void sqlite3VdbePreUpdateHook(
   const char *zDb,                /* Database name */
   Table *pTab,                    /* Modified table */
   i64 iKey1,                      /* Initial key value */
-  int iReg                        /* Register for new.* record */
+  int iReg,                       /* Register for new.* record */
+  int iBlobWrite
 ){
   sqlite3 *db = v->db;
   i64 iKey2;
@@ -5225,6 +5226,7 @@ void sqlite3VdbePreUpdateHook(
   preupdate.iKey1 = iKey1;
   preupdate.iKey2 = iKey2;
   preupdate.pTab = pTab;
+  preupdate.iBlobWrite = iBlobWrite;
 
   db->pPreUpdate = &preupdate;
   db->xPreUpdateCallback(db->pPreUpdateArg, db, op, zDb, zTbl, iKey1, iKey2);

src/vdbeblob.c

@@ -420,7 +420,7 @@ static int blobReadWrite(
       sqlite3_int64 iKey;
       iKey = sqlite3BtreeIntegerKey(p->pCsr);
       sqlite3VdbePreUpdateHook(
-          v, v->apCsr[0], SQLITE_DELETE, p->zDb, p->pTab, iKey, -1
+          v, v->apCsr[0], SQLITE_DELETE, p->zDb, p->pTab, iKey, -1, p->iCol
       );
     }
 #endif